How to Think about the Internet of Things (IoT)

Many people have tried to define the Internet of Things. But as a hardware or software engineer, you already know the essential element: to build interconnected products.

Embedded systems are already playing a crucial role in the development of the IoT. In broad strokes, there are four main components of an IoT system:

The Internet of Things from an embedded systems point of view

The Internet of Things from an embedded systems point of view

IoT systems are not complicated, but designing and building them can be a complex task. And even though new hardware and software is being developed for IoT systems, we already have all the tools we need today to start making the IoT a reality.

We can also separate the Internet of Things in two broad categories:

So to better understand how to build IoT devices, you first need to figure out how they will communicate with the rest of the world.

Your Local Network

Your choice of communication technology directly affects your device’s hardware requirements and costs. Which networking technology is the best choice? IoT devices are deployed in so many different ways — in clothing, houses, buildings, campuses, factories, and even in your body — that no single networking technology can fit all bills.

Let’s take a factory as a typical case for an IoT system. A factory would need a large number of connected sensors and actuators scattered over a wide area, and a wireless technology would be the best fit.

Wireless sensor network installed in a factory, connected to the Internet via a gateway

Wireless sensor network installed in a factory, connected to the Internet via a gateway

A wireless sensor network (WSN) is a collection of distributed sensors that monitor physical or environmental conditions, such as temperature, sound, and pressure. Data from each sensor passes through the network node-to-node.

WSN Nodes

WSN nodes are low cost devices, so they can be deployed in high volume. They also operate at low power so that they can run on battery, or even use energy harvesting. A WSN node is an embedded system that typically performs a single function (such as measuring temperature or pressure, or turning on a light or a motor).

Energy harvesting is a new technology that derives energy from external sources (for example, solar power, thermal energy, wind energy, electromagnetic radiation, kinetic energy, and more). The energy is captured and stored for use by small, low-power wireless autonomous devices, like the nodes on a WSN.

WSN Edge Nodes

A WSN edge node is a WSN node that includes Internet Protocol connectivity. It acts as a gateway between the WSN and the IP network. It can also perform local processing, provide local storage, and can have a user interface.

WSN Technologies

The battle over the preferred networking protocol is far from over. There are multiple candidates.

Wi-Fi

The first obvious networking technology candidate for an IoT device is Wi-Fi, because it is so ubiquitous. Certainly, Wi-Fi can be a good solution for many applications. Almost every house that has an Internet connection has a Wi-Fi router.

However, Wi-Fi needs a fair amount of power. There are myriad devices that can’t afford that level of power: battery operated devices, for example, or sensors positioned in locations that are difficult to power from the grid.

Low-Power Solutions

Newer networking technologies are allowing for the development of low-cost, low-power solutions. These technologies support the creation of very large networks of very small intelligent devices. Currently, major R&D efforts include:

For example, EnOcean has patented an energy-harvesting wireless technology to meet the power consumption challenge. EnOcean’s wireless transmitters work in the frequencies of 868 MHz for Europe and 315 MHz for North America. The transmission range is up to 30 meters in buildings and up to 300 meters outdoors.

IEEE 802.15.4

One of the major IoT enablers is the IEEE 802.15.4 radio standard, released in 2003. Commercial radios meeting this standard provide the basis for low-power systems. This IEEE standard was extended and improved in 2006 and 2011 with the 15.4e and 15.4g amendments. Power consumption of commercial RF devices is now cut in half compared to only a few years ago, and we are expecting another 50% reduction with the next generation of devices.

6LoWPAN

Devices that take advantage of energy-harvesting must perform their tasks in the shortest time possible, which means that their transmitted messages must be as small as possible. This requirement has implications for protocol design. And it is one of the reasons why 6LoWPAN (short for IPv6 over Low power Wireless Personal Area Networks) has been adopted by ARM (Sensinode) and Cisco (ArchRock). 6LoWPAN provides encapsulation and header compression mechanisms that allow for briefer transmission times.

Wireless radio technologies
Standard IEE 802.15.4 Bluetooth WiFi
Frequency 868/915 MHZ, 2.4 GHZ 2.4 GHz 2.4, 5.8 Ghz
Data rate 250 Kpbs 723 Kpbs 11 to 105 Mpbs
Range 10 to 300 m 10 m 10 to 100 m
Power Very Low Low High
Battery Operation Alkaline (months to years) Rechargeable (days to weeks) Rechargeable (hours)

There are many wireless networks available that are specialized for various industries. The following is a brief list:

6LoWPAN DASH7 Wireless M-Bus
ANT ISA100 Z-Wave
Bluetooth Wireless HART Zigbee and Zigbee IP

And there are many more.

At Micrium, we believe that any protocol that carries IP packets has an advantage over all others. The connectivity requirements for IoT devices are so diverse that a single technology cannot meet all the range, power, size and cost requirements. Nonetheless, we believe that 6LoWPAN will be the choice for WSNs and light IP-based protocols (see next section).

IPv6 is Key for IoT

If your IoT network is local and M2M-only, then the wireless protocols discussed above are all good candidates. But if your goal is to remotely control devices or otherwise transmit data over the Internet, then you need IPv6.

The usefulness of IoT devices resides not only in local communication, but also in global communication. If at all possible, it is crucial that your IoT networks (LANs, PANs, and BANs) all make use of the suite of Internet Protocols (IP, UDP, TCP, SSL, HTTP, and so on). Furthermore, your networks must support Internet Protocol version 6, as the current IPv4 standard faces a global addressing shortage, as well as limited support for multicast, and poor global mobility.

IPv6’s addressing scheme provides more addresses than there are grains of sand on earth — some have calculated that it could be as high as 1030 addresses per person (compare that number to the fact that there are 1028 atoms in a human body!). With IPv6, it is much simpler for an IoT device to obtain a global IP address, which enables efficient peer-to-peer communication.

The importance of IP to the Internet of Things does not automatically mean that non-IP networks are useless. It just means that non-IP networks require a gateway to reach the Internet.

Referring back to the illustration at the top of the page, you can see clearly that your local network is only one part of the Internet of Things. 6LowPAN, because it carries an IPv6 address with a compressed header, offers Internet connectivity without too much additional overhead. 6LoWPAN has also an advantage over other personal area networks, because peer-to-peer communication is simpler to implement when each device has a global address.

Additional References

http://postscapes.com/internet-of-things-protocols